add constructor for spaces service

Also adds a public function to invalidate the cache rather than exposing
the entire cache publicly.

src/service/rooms/state.rs

@@ -103,10 +103,8 @@ impl Service {
                     services()
                         .rooms
                         .spaces
-                        .roomid_spacechunk_cache
-                        .lock()
-                        .await
-                        .remove(&pdu.room_id);
+                        .invalidate_cache(&pdu.room_id)
+                        .await;
                 }
                 _ => continue,
             }